Once the PV site evaluation and load analysis have been completed, two types of design/build options are available: Design-Bid-Build and Design-Build. In the Design-Bid-Build method, the full PV design is completed first and then put up for competitive bid. Many municipalities favor this option because it provides more of an opportunity to compete on price.
However, this delivery method requires a longer schedule time and limits the contractor from providing constructability input during design that can add value and flexibility to the project.
With the Design-Build method, the PV design is taken only to a schematic level identifying performance requirements and general parameters. Here, the contractor chosen will complete the design while building the PV on site, as the design engineer oversees the project for the owner. With this method, the overall schedule time is often reduced, as the contractor can start working sooner and make appropriate design decisions on the job. This can lead to reduced cost and more efficient ways of designing a PV because no one is restricted by a full design.
While photovoltaics (PVs) help offset energy costs and simultaneously exhibit a strong environmental commitment, they are not appropriate for every airport.
1. Cost Effectiveness and ROI – Very often with city-owned airports, employing a PV can be a community-wide political issue. When this is the case, the airport may be willing to accept a longer payback period.
2. Maintenance – While maintaining PV panels are a consideration for any type of building, airport PVs have a unique air quality challenge as a direct result of the jet fumes, ground support equipment, and passenger vehicle traffic they are subject to on a regular basis. A maintenance program must be set in place to maintain the cleanliness of the solar panels in order to ensure they can operate at maximum efficiency.
3. Climate – Airport or office building, PVs are only going to make a real difference in harvesting usable energy in a year-round, sunny climate.
4. Carbon Footprint Reduction – In order to calculate how much carbon footprint reduction a PV array will lead to, projected energy savings must be calculated. Carbon reduction calculations need to include not only the energy saved from the operation of the PV system, but should also embody the energy and carbon required to manufacturer, transport, and install the PV or other related equipment.
5. Existing Airport vs. New Construction – When installing renewable energies at an existing airport, energy expenditure pre-installation can be compared to post-installation to determine real savings over time, as compared to new construction where the energy savings is assimilated. That being said, space constraints often plague PV instillations in existing airports, while new construction typically lends itself to more flexibility for PV installations.
6. Panel Angle and Direction – It is crucial that design engineers conduct studies on the angle of the sun versus the angle and direction of the panels to determine optimal PV panel orientation.
About the authors
Lalit N. Mehta, P.E.
A member of the Airport Consultants Council (ACC), the American Associations of Airport Executives (AAAE), and the American Society of Heating Refrigeration and Air Conditioning Engineers (ASHRAE).
Carl Newth, PE, LEED AP BD+C
An active member and serves on committees of the Airport Consultants Council (ACC), the American Associations of Airport Executives (AAAE), American Society of Heating Refrigeration and Air Conditioning Engineers (ASHRAE), and the FAA’s NextGen Working Group.
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